Electric-circuit-protecting apparatus



B. M. MOOERS 'AND E. WARNER.

ELECTRIC CIRCUIT PROTECTING APPARATUS.

APPLICATION FILED MAR. I. I9l8 1,381,581 Patented June 14, 1921. Q 2 $HEETS--SHEET1| WITNESS Q BIN V ENTOR. 1

' g g N 1M5. WARNER v MW I By ATTORNEKS B. M."M0 0ERS AND L. E. WARNER. ELECTRIC CIRCUIT PROTECTING APPARATUS. APPLICATION man MA". 1, 191a. 1,381,581 Patented June 14, 1921.

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Specification. of. Letters Eatent.

lPatented June it, 1921..

application filed march ."Q, 1912;. .Zverial' Tito. QLKEJMS,

To all 'whomet may concern: 7

Be it known that we, BENJAMIN M, Miocene and liawnnnon E. WARNER, citizens of; the United States, and residents, respectively, of the city and county of San Francisco, and of Berkeley, county of Alameda, both in the State of California, have invented a certain new and useful Electric-Circuit-l?rotecting Apparatus, of which the following is a specification.

lhe invention relates to apparatus for opening an electric circuit when certain electrical condi ions obtain in said circuit.

An object of the invention is to provide an apparatus which is operated either by a deleterious overload on the electrical apparatus in circuit or a decrease or voltage in the circuit below a given voltage, to open the circuit.

A further object of vthe 'rovide means for preventing the circuit roin being closed and held closed when either the voltage or overload conditions mentioned exist.

The invention possesses other advantage invention is to ous features, some of which, with the fore going, will be set forth at length in the fob lowing" description where we shall outline in full that formiofthe invention which we have selected for illustration in the draw ings accompanying and forming part of the present specification. In said drawings we have shown one specific form of the appa ratns of our invention, but it is to he understood that we do not limit ourselves to such form, since the invention, as expressed in the claims, may be embodied in a plurality of forms.

Referring to said drawings:

' Figure 1 is a side elevation of one form of apparatus of our invention, the switch being shown open. 4

Fig. 2 is a front elevation of the apparatus shown in Fig. 1.

Fig; 3 is a diagrammatic representation oi: the electric circuits of the apparatus.

The apparatus of our invention is a r-" ranged in the circ :t of the electrical appacred and is designed to open the circuit when an overload which would be deleterious to the apparatus obtains, and when the volts of the supply circuit falls below predetermined rninininnu. The overload which would he deleterious to the appathe niotor circuit, and the ratusis preferably measured by the ten1pcratnre which it produces in the apparatus or a selected portion thereof, and with the same current flowing in the device and in the appara-tus when the predetermined maximum temperature obtains in the hottest part of the apparatus, the device of our invention operates to open the circuit.

in the present instance we will assume that the apparatus to be protected is the three phase alternating current motor M which is supplied with current from the generator The generator leads 3 and 4 are connected to the lower ends of the switch blades 5, 6 and 7. lhe switch blades are adapted to contact respectively with the contact clips 12., 13 and la: the motor li'l. Arranged in two of the motor leads are thermostats of any suit able type which when heated to a predetermined temperature operate to release the .switch and cause it to open the circuit. In

the present construction, each thermostat consists of a metallic bar 15, fixed at its lower end and pivoted at its upper end to the. lever 16. The lower end of the bar 15 is connect ed to the contact clip 01% the switch and con nected'to and surrounding the bar is a heat- .ing coil 17, the free end of which is connected inthe motor circuit. w lhe bar and the heat-- ing coil are therefore arranged in series in heating coil is made oi such and material and is so in sulated from the surrounding; atmosphere, that with the same current in the heating coil and in the motor winding the temper ture of the bar corresponds directly at alltinies during thcoperation of the motor with the tern.- perature of the hottest part of the windings. of the motor.

stationarycontact 18, to which the" ends of the electrolnagnet coil 19 are connected. The lovers are electrically connected to the generator when the switch is closed and there :tore when the levers engage the contacts 18, the electromagnet is connect ed across the generator. The resistance or reactance oi the electrornagnet, however, is such that only a small current-passes through the electr magnet, but as long as the temperature con- I ditlons in the thermostats are normal or below a predetermined maximum, the levers 1.6 remain in engagement with the contacts which are connected to -Arranged adjacent to andv normally 1n contact with each lever 16, is a 'tion of motor windings increase above a predetern ined temperature, the temperature of one or both of the thermostats Wlll increase, causing an elongation of car 1.5,

which. moves the lever 16 out of engagementv with the contact 18, and thereby opens the circuit of the electromagnet. Associated with the electromagnet is an armature 21 which is held in a raised. position by the flux in the energized electromagnet and when the circuit of the electromagnet is broken, the armature falls. Should the voltage in the circuit decrease, the pull of the electromagnet decreases, and the weight of the armature so chosen, that when the voltage in the circuit reaches predetermined minimum, the armature will fall.

The armature is associated with the switch. in the circuit, so that-when the armature falls, the. switch is opened. The switch blades are connected together by a bar 22 of insulating material and are held in closed position against the force oil the opening spring 23 by the pivoted latch. 24: which ongages the cross bar 22. Extending overthe latch 2% is an arm to which is pivoted a trigger 26, which engages in a slot 27 in the latch. The free end of the trigger ex tends upward above the arm and lies in the path of the armature 21, which is pivoted to the frame 28. When the armature falls, it strikes the trigger 26, causing the latch to I he raised and the switch tohe released. The

Weight of the armature is suflicicnt to hold the trigger depressed and the latch raised.

Means are provided for preventing the switch from being closed and. held closed when the electromagnet circuit is open or when the supply voltage is below the mini mum. The switch is inclosed in a locked case 29, so that access may not he had to it directly. Concentric i i h the pivots of the switch blades is a shaft 31 which extends through the case and which is provided on its outer end with a handle 32. Secured to the shaft 31 within the case or formed integrally therewith, is an arm 33 which is provided on its outer end with a spring-pressed latch 3t which is adapted to engagea clip on the cross bar of the switch. The handle is normally in its downward position, so that when the switch flies out, the clip 35 comes in contact with the latch By raising the handle, the switch is moved back to the closed position, but unless normal conditions exist in the apparatus and in the supply circuit, the switch will immediately fly out.

The latch 34 is provided with an arm 36 which when raised raises the latch out of contact with the clip 35, allowing the switch to spring back. Formed on the latch 04 is a curved projection 37 substantially concentric with h e center ct rotation of the shaft 31, over which the pin 88 on end of the arm 36 moves as the liai'idle is moved to bring the switch to closed position. cured the a oo. 33 is an extension 39 pro vidcd on its end with a blade d2, which, as "the arm 33 raised. passes under the l" l3 on. the armature and the arm into contact with the 'clectromagnet, a5 ing the latch to drop and the ti," to rise. The blade 12 is of such len it moves out of contact with the la" the same time that the switch hlud with the switch contacts. In. the 1 I the electron nct circuit mostat or t rat the volta r mature will drop onto the trigger 26, rair. the latch 2 and its extension 3%), which will raise the latch iii l and allow the switch blades to fly back. Should line and ripper tus conditions he pr p...r, the armature remain in. contact with the elcctroinup nct, the latch 24.- will and hold the switch and the handle may he moved back to its lower position. The latch 48 in the armature is preferably constructed the ordi nary spring-pressed door latch, so that it springs back out of the path of the blade 42 when the handle returned to its lower position.

Vi e claim:

1. it protective device for an electric cir cuit containing electrical apparatus, comprising an electromignet connected acres said circuit switch in said circuit, means operative by the opening; oi the clcctronu f not circuit for opening; said switch, means controlled by the load on the apps atus for opening said elcctromagnet circuit, lit. die for returning the switch to closed position and means operative duri; that the electromagnct circuit releasing the switch from th electric 4:. cult containing elec rical apparatus, i prising an electromagnet connected across said circuit, a switch in said circuit, means operative by a decrease in flux in said electromaguct to a predetermined minimum to open said switch, means operative by the current in the circuit "for opening the switch, means for returning the switclji to closed position, and means operative during the presence of said minimiun llux for preventing the operation of the switch closing means.

3. A 'giiroter-tive device for an electric circuit containing; electrical apparatus, cone prising a switch in said circuit, means oper ated by a reduction of voltage in said circuit to a predetermined value to open said switch, means controlled by the load on the apparatus to open said switch, a handle for closing said switch and means operative dun the presence oi the low voltage in the cimil ml aiming the pissiice m? in 6%?! load on the apparatus 01. releasing the switch from the handle.

ll A pretcctivs dcvics for an electric ci1fcontaining Qlili'b- '1] zqupzu'atus, comisiziigmc in the thermustzit ainl din-111g;- l of the low vcltsgc m m yloscm, it casing the switch from ihc 1'5 device for an. electric clcc romsgnct connecizcll Huh, :2 switch in said circuit, am mrmaturs associated with said electromagnet and mhiptcil to fall and lcleasc said switch when ch's in through. the electinmagmas L reaches a, If/IQQChQIfHlihUl minimum, 2L handle {or returning the switch in closcxl position and means cpcmtivc by the closhiig of ills handls for releasing the 1mm this has is when the flux. said minigiuu we 6. A. proiective device iror an electric cir- Quit, comprising an. clecti'oma-gnet mi'anged in said circuiafi, a switch in said, circuit, an armature associated with said clecti-omngnct and adapted when released from said electnnnngnct t0 fall and release said switch, and means for simultaneously raising said arnmtui'e :unl closing SZ'LiLl switch.

7: A protective device for an electric circuit comprising an clectvi'omagnct a1 anged in said chic-nil, :1 switch. in said circuit, an m'nmturc associated with said elecm'omugnct and adapted when l "mm said elucsi'onmgnict l1:- flall and iclcase said switch, and n'iczms for simnllizmemzsly i'nisii'ig said zu-nmhu'e and moving said switch toclosed pcsiticn, said. means lacing consm-uctccl to permiti-mill m'izmtmc to drop and i-clcase iii s switch from the losing means when the Flux in sziiil clci'ztrmnagnct is below a preletcrn1ine-;l minimum.

in testimuny whereof we have hereunto 0111* hands at Sam ifix'mlcisco, California this 30th day (if ,Eapmu'y, 191.8, and this 9th day of .Fchiiizuyf 1918, respectively.

LEQVR ENCE E. \VAR N 131R.

in pressncc. 0't'--- 

